A corona charging method has been used as a charging method of an image forming apparatus which adopts electrophotography method, electrostatic recording method, and the like.
The corona charging method is performed in such a manner that: ion caused by corona discharge is led to a surface of an electrostatic latent image carrier of a photoconductor and the like, thereby charging the surface. As such, when charging is performed repeatedly, O3 and NOx generated in corona discharge, toner, paper powder, and the like float near the corona charger. This causes the corona charger to unevenly charge the surface of the image carrier, with a result that defective images are formed.
For example, in a case of a pin array charger which is a kind of the corona charger, foreign matters such as O3 and NOx are attached to an end of a discharge needle, so that the end of the discharging needle causes discharge inhibition and charge unevenness. As a result, defective images are formed. The same phenomenon occurs in a case of a wire charger. This is because: the corona charger discharges electricity while collecting air including the generated O3 and NOx, and floating matters such as toner and paper powder which float in the image forming apparatus.
Therefore, Document 1: Japanese Unexamined Patent Publication No. 026731/1997 (Tokukaihei 09-026731; published on Jan. 28, 1997) discloses an image forming apparatus including exhausting means for exhausting O3, NOx, and the like floating near an image carrier.
Further, Document 2: Japanese Unexamined Patent Publication No. 206841/2000 (Tokukai 2000-206841; published on Jul. 28, 2000) discloses an image forming apparatus including a blowing fan for blowing air to charging means and an intake fan for bringing in air near the charging means.
However, Document 1 has such a problem that: means for removing O3, NOx and the like floating near the image carrier is only the exhausting means and accordingly it is impossible to sufficiently remove O3, NOx and the like.
Further, Document 2 has an arrangement in which the blowing fan and the intake fan are disposed so that the fans are positioned near to each other. As a result, even when an intake fan brings in O3, NOx and the like near a first charger, a blowing fan disposed near the intake fan blows air containing a bit of O3, NOx and the like to the first charger and vicinity thereof. Therefore, as the first charger gets used more frequently, more amounts of O3, NOx and the like are accumulated at the first charger and vicinity thereof, resulting in charge defect in the first charger.
Document 3: Japanese Unexamined Patent Publication No. 163770/2004 (Tokukai 2004-163770; published on Jun. 10, 2004) discloses a technique in which air flows through an absorbing material including polar absorbent, thereby removing materials generated as a result of discharge in charging an image carrier. Further, Document 4: Japanese Unexamined Patent Publication No. 196635/2002 (Tokukai 2002-196635; published on Jul. 12, 2002) discloses a technique in which: openings are provided at both sides of a shield case so as to be positioned in a long side direction, and a blowing fan is provided at one opening and an intake fan is provided at the other opening, and air is caused to flow in a direction in which a charging wire is extended, thereby removing and exhausting materials generated as a result of discharge.